Due to their excellent moldability, mechanical characteristics, electrical properties, etc., polyolefin-based resins are used in various fields as materials for film molding (i.e., molding for production of films), sheet molding (i.e., molding for production of sheets), blow molding, injection molding, etc. Although physical properties are generally excellent, such polyolefin-based resins have the problem of having low transparency, crystallizability and rigidity.
There have heretofore been proposals to use amide-based compounds, etc. as a nucleating agent so as to solve these problems (Japanese Unexamined Patent Publication No. 1994-192496, Japanese Unexamined Patent Publication No. 1995-242610, Japanese Unexamined Patent Publication No. 1995-278374, and Japanese Unexamined Patent Publication No. 1996-100088). When polyolefin-based resin compositions containing such amide-based compounds are molded, molded products with excellent transparency and mechanical strength can be obtained.
However, in order to obtain molded products with such outstanding characteristics in commercial production, the molding conditions need to be optimized according to the molding method to be adopted.
The molding methods include injection molding, extrusion molding, sheet molding, film molding, blow molding, etc. Molded product manufacturers must appropriately determine the molding conditions (injection or extrusion rate, injection pressure, resin temperature, mold temperature, chill roll temperature, shape of molds, etc.) of the molding machine according to the molding method, so as to optimize the processing conditions.
However, optimization of such molding conditions takes much time since many variables need to be determined, and the determination thereof is complicated. When such molding conditions are not determined correctly, the following problems may occur: white spots originating from non-dispersed nucleating agents may appear in the molded products, the transparency of the molded products may be inferior, the mechanical strength of the molded products may be weak, etc.
It is also known that certain nucleating agents elevate the crystallization temperature of polyolefin-based resins to some extent, and the molding cycle time can be shortened by using such nucleating agent. However, the use of such nucleating agent merely results in a crystallization temperature peculiar to the use of such nucleating agent, and the crystallization temperature cannot be controlled. Therefore, the use of such nucleating agent currently does not greatly contribute toward facilitating and expediting the setting of molding conditions or diversification and flexibility of the processing conditions.